The invention relates to a driving mechanism for oscillating displacement pumps. Such driving mechanisms are known from British Pat. No. 1,442,500. In these known driving mechanisms the time sequence of the volume flow and of the suction pressure as well as of the discharge pressure is determined by the geometry of the pole shoes and of the field configuration. Thus, among others, the flow speed is also determined.
When conveying media which can withstand only a certain reduced pressure or increased pressure without damage, it is necessary to reduce the driving speed of such pumps so that the occurring reduced or increased pressures do not exceed the permissible limit values. Thus, the mass flow is substantially reduced and the pump is insufficiently utilized. However, it is possible to reduce these difficulties by using volume storage means in the form of expansion chambers arranged upstream or downstream, whereby the entire pumping system becomes more involved and more expensive. Besides, by these features it is not excluded that the permissible reduced or increased pressures are exceeded anyway. Additionally, these features cause an increase in the volume of the medium being conveyed in the pump conveying system.
In connection with media to be conveyed which may not be exposed to certain maximum shearing stresses, it is necessary to keep the acceleration forces of the moving pump components so low that the limit value of the shearing stress is not exceeded at any points of the hydraulic system. This also reduces the degree of efficiency of the pump.
It is known in connection with positioning means for disc memories in the data processing art, which comprise electro-dynamic linear motors, to provide a control circuit which controls the positioning stroke in response to the difference between the actual value of the positioning displacement and the reference value of the desired position as well as in response to the positioning speed. However, in connection with such positioning means for disc memories used in the electronic data processing art, problems of quite a different type occur. Especially, it is essential that the desired reference position is reached precisely so that this known device could not provide any hints with regard to driving mechanisms for oscillating displacement pumps ("Feinwerketechnik and Mikronik", Vol. 77, Nr.4 1973, pages 151 to 157).